What are Biosolids?
Biosolids can be safely applied to soil as a fertilizer and/or soil conditioner to improve and maintain agricultural and forest lands as well as to restore damaged acreage. Biosolids is the final product, safe to recycle and rich in plant available nutrients, created through multiple processes and scientifically-advanced treatment of sewage sludge generated by thousands of Publicly-owned municipal water treatment facilities all across the country.
Since every community of any size must process the wastewaters generated by its population, recycling biosolids for added benefit to agriculture and horticulture makes sense. Created during the past 30 years, the biosolids process has resulted in the rapid and remarkable cleansing and restoration of America’s rivers and streams.
How does the process work?
Publicly-owned municipal wastewater treatment facilities use the same processes that nature uses to clean the environment. In streams and lakes, natural aeration helps to purify the water, while microorganisms break down solids. Wastewater treatment plants use settling basins, aeration tanks and digestion or lime to reduce the pathogens—organisms that cause disease—and break down solids.
Municipal treatment facilities require pretreatment measures from businesses and industries to reduce contaminants from wastewater before it enters the sewer system. Once wastewater is conveyed to a typical treatment facility, “grit materials” (such as sticks, rags and pebbles) are removed. The wastewater is next allowed to sit in large sedimentation tanks, where some solids settle to the bottom and are collected. The wastewater then continues on for digestion in large tanks where natural beneficial microbes are used to consume and break down wastes and nutrients. These microbes and other solid particles settle to the bottom of the tanks where they are collected. The cleaned wastewater may then receive additional treatment before it is disinfected and returned to waterways.
The solids that are collected from the primary and secondary treatment processes, called sludge, are collected and may undergo further biological treatment or lime stabilization to further decompose the material and destroy any potential disease organisms. These treatment processes reduce odors and destroy most of the potentially harmful pathogens contained in the solids. These treated, stabilized solids are now called biosolids and are mostly organic matter and minerals.
Biosolids, in liquid or dewatered form (called “cake”), are ready to be returned to the environment as a fertilizer and soil conditioner. Biosolids can be recycled directly on soils in the forest, on agricultural land, or can be composted and used for landscaping and gardening.
Who has the expertise?
Synagro believes that organic waste streams should be recycled as safely and responsibility as possible. We work day in and day out to utilize biosolids and other organic materials in ways that protect the environment and benefit agricultural systems. Our programs for municipal and industrial customers assist in the reduction of pollution in our environment and have helped to improve the country’s water quality more than anything else to date.
The Synagro nationwide team is fully committed to environmental protection, high standards of operations and meeting and/or exceeding all regulatory requirements. Synagro’s services and operational practices consistently conform to both regulatory requirements and the broader commitment to address all aspects of protection of the environment.
Synagro is one of the largest and most technically-competent companies in the biosolids industry and provides over 600 municipalities and industrial customers with environmentally responsible organic residual management services. Many municipalities manage their own waste treatment and have recycling and land application programs. Others choose to contract with companies like Synagro to take advantage of specialized expertise and more advanced technology.
All of us at Synagro are proud to be an active part of helping to create a more sustainable environment.
Specific Benefits of Biosolids Recycling
The organic matter in biosolids improves soil quality, reduces compaction, increases water-holding capacity, and provides an energy source for necessary microbial activity. This reduces water runoff and soil erosion, increases water conservation and increases resistance to drought. Biosolids that have been lime-stabilized help neutralize acidity in soils, just as is done by agricultural limestone, which helps maintain the proper soil pH for crop growth.
Chemically, biosolids increase the soil’s cation exchange capacity (CEC), which is a measure of how well a soil retains certain plant nutrients. The organic matter in biosolids acts like a magnet and attracts plant nutrients. It helps hold plant nutrients in the root zone and prevents them from leaching.
Recycling
- EPA supports the land application of biosolids as a safe recycling method. Recycling biosolids to the soil is beneficial for farms, forests, and landscaping. The process can improve site conditions in many ways and help the environment.
Community Benefits
- Biosolids land application carries many economic and
environmental benefits. It not only saves local and state governments
significant amounts of money through lower disposal costs and sales of
biosolids-derived products, but it also adds nutrients and positive soil
characteristics to agricultural land.
- More
than $2 billion is spent annually treating and managing approximately 5.3
million dry metric tons of biosolids from publicly-owned wastewater treatment
plants in the
- Land application improves the surrounding environment by reducing pollution and increasing soil productivity. Because biosolids provide nutrients in an organic form, they are utilized by the crops instead of lost to adjacent streams and groundwater. Therefore land application reduces and eliminates pollution that is often caused by traditional fertilization methods. The organic matter supplied by biosolids builds soil structure to reduce soil erosion and increase vegetative growth.
Cost Benefits
- Land application of biosolids costs less than half of the next available alternative (usually using landfills). The savings realized by municipalities are passed on to communities in the form of reduced taxes along with lower sewer and water bills.
- Farmers can save up to $150 per acre of biosolids applied land. This translates into thousands of dollars per year depending on the amount of land utilized. This support of local farmers allows them to produce food more affordably which keeps the prices at the grocery store down.
Water Quality Protection
- Biosolids recycling programs carry restrictions on the application amount and location of where biosolids can be applied to protect environmentally-sensitive areas and to prevent groundwater contamination. EPA estimates that every day about 1.2 trillion gallons of contaminated water seeps into the ground in the United States from septic tanks, landfills, forests, agricultural land and abandoned wells. Contamination from many of these sources is caused by the lack of controls and restrictions to protect environmentally-sensitive areas.
- Studies have shown that fields applied with biosolids have less runoff of nutrients and pollutants than with commercial fertilizers and animal manures. Additionally, site restrictions such as requiring minimum buffers around streams and other water bodies further reduce the potential for pollutants to enter surface waters.
Landfill Space Reduction
- More
than 1,200 of the existing 1,500 landfills in the
Landscaping and Gardening Enhancement
- Biosolids sold in stores can be used on home and community lawns and gardens to provide nutrients and organic matter. Biosolids are also used on golf courses, public parks and recreational areas.
Soil Erosion Reduction
- Recycling biosolids helps prevents soil erosion because it consists mainly of organic matter. Organic matter is the most significant factor in giving the soil a spongy texture so it holds water and nutrients preventing them from running off and causing erosion. Many farms can lose as many as 10 tons of topsoil per acre per year as a result of continuous cropping. In addition, soil erosion and runoff from agricultural fields are the largest cause of water pollution in the United States.
Contaminated and Stripped Land Site Reclamation
- Biosolids has been used successfully to reclaim strip-mined lands. Abandoned coal mines and gravel pits leave exposed rock and subsoil which contributes to runoff and water contamination. Biosolids provides nutrients and topsoil which allows a protective vegetative cover to grow and renew the disturbed land.
Natural Nutrients Supply
- Plants need a complex mixture of nutrients, soil, air
and water. Biosolids contain many essential plant nutrients, including the
primary macronutrients nitrogen, phosphorus, and, to a lesser extent,
potassium; the secondary macronutrients magnesium, calcium and sulfur; and
such micronutrients as copper, zinc, iron, manganese, molybdenum and boron.
Humans also need many of these elements, which are contained in
multi-vitamins.
- Since commercially-applied nitrogen is immediately
available to the crop, anything the plant cannot use is carried away by storm
water or leached to the groundwater.
- Biosolids provide an organic form of nitrogen which releases the nitrates as the plant needs them – reducing and eliminating the potential for contamination of drinking water. The micronutrients provided by biosolids are also held in the topsoil, allowing them to be available for crop use instead of being carried away by storm water.
- Biosolids contain the nutrients the soil and plants need, so there is no need for farmers to buy and apply additional nutrient – saving the farmer up to $150 per acre.
Increased Crop Yields
- Biosolids fertilization often increases crop yield,
especially in severely-eroded cropland and sandy soils.
One farmer cites a 141-acre field adjacent to his home. In past, the field’s best yield was about 40 bushels per acres because of the soil type and shallowness. Through use of biosolids, the field yielded over 55 bushels per acre.
- Testing
plots at Virginia Polytechnic Institute and
Forestry Benefits
- Biosolids have been found to promote rapid timber growth, allowing quicker and more efficient harvest of an important natural resource.
- Forestlands are ideal for biosolids application. They can be applied at different stages of growth including to land before planting, to seedlings, and to older trees that have been thinned.
- Forests absorb runoff from rain and snow, trees take up nutrients year-round, and forest soils include a great deal of organic matter from decayed foliage, bark, branches, and trunks which holds nitrogen in place until plants can use it.
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